Transmission for a working vehicle

ABSTRACT

In a transmission for a working vehicle, a working unit includes a hydraulic power unit and a valve unit enclosed in a first bulging portion of a transmission case closer to an upper side or on a top surface thereof and connected with each other along a vehicle lengthwise direction. The first bulging portion is closer to a first lateral side along the vehicle width direction of the transmission case, while a hydraulic pump is located closer to a second lateral side. Hydraulic fluid is drawn from the transmission case, around a lower side of the hydraulic pump, through a suction port thereof, and discharged to a suction port of the valve unit. The hydraulic power unit includes a cylinder tube and piston, extending in the lengthwise direction, and a support shaft, extending along the width direction, which is supported by the transmission case and connected to a lift arm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power transmission arrangement in aworking vehicle with a working unit such as a cultivating unit and mowerunit attached thereto, and a transmission for the working vehicle.

2. Related Art

In a vehicle equipped with a working unit such as a bucket, cultivatingunit and mower unit on the front side, rear side and/or below thelengthwise center of a chassis, driving power from a driving powersource must be divided into a running power transmission path and adriving power transmission path for working unit so as to be transmittedto driving wheels and the working unit. This poses a problem ofincreasing a size of the transmission in the vehicle.

For example, Japanese Patent Application Publication No. Hei-01-17883and Utility Model Application Publication No. Hei-01-37298 disclosearrangements, which are applicable to the vehicle of the above type, fordownsizing the size of the transmission.

The transmission disclosed in each of the above-cited publications hasan input shaft for the working unit (PTO input shaft) and a runningpower input shaft, which are respectively aligned in vertical andparallel relationship with each other, and a transmission case in whichthe power transmission path for working unit and the running powertransmission path are arranged respectively closer to upper and lowersides thereof with occupation of spaces as much compact as possible inan attempt to reduce the size of the transmission.

Meanwhile, for the vehicle equipped with a working unit as mentionedabove, a hydraulic power unit for operating the working unit must beprovided in some cases, in addition to a power-take-off arrangement fortaking off driving power for the working unit. As such a hydraulic powerunit, it can be cited a hydraulic lift unit for lifting a cultivatingunit mounted on the rear side of the chassis.

As described above, in each of the above-cited publications, althoughthe downsizing of the transmission may be achieved by arranging therunning power transmission path and the power transmission path forworking unit within the transmission case respectively closer to theupper and lower sides thereof with occupation of spaces as much compactas possible, such downsizing was not considered for the transmission ofthe vehicle provided with the aforesaid hydraulic power unit.

Specifically, in a vehicle disclosed in each of the cited publications,a hydraulic power unit for reciprocating a cultivating unit or any otherworking unit is disposed on a top surface of the transmission, while ahydraulic pump for feeding pressurized fluid to the hydraulic power unitis supported on a rear wall of the transmission case.

More specifically, in the transmission described in each publication, aclutch shaft and an intermediate shaft, which constitute a part of thepower transmission path for working unit (PTO system), extend below andon the opposite lateral sides of a PTO input shaft, so that an upperspace of the transmission case is occupied by this PTO powertransmission path. Accordingly, in this conventional transmission, it isnot possible to secure within the transmission case closer to the upperside a space for accommodating the hydraulic pump for feedingpressurized fluid to the hydraulic power unit, a driving powertransmission mechanism for the hydraulic pump, etc. For these reasons,the conventional transmission has the hydraulic pump supported on therear wall of the transmission case and a rear end of the PTO input shaftextending through the rear wall of the transmission case, through whichthe hydraulic pump is driven.

Thus, for the vehicle equipped with the hydraulic pump, the hydraulicpump of the conventional transmission extending rearwards through thetransmission case poses a difficulty in shortening the length of thetransmission with the hydraulic pump.

Also, according to the above arrangement, working fluid reserved in thetransmission case for the hydraulic power unit is once transmittedaround the rear side of the transmission case and then to the upper sideof the transmission case. Accordingly, a hydraulic fluid circulationpath to the hydraulic power unit must be elongated, which necessitatesapplication of an excessive load to the hydraulic pump.

As another disadvantage involved in the vehicle described in each citedpublication, since the hydraulic power unit is disposed on the topsurface of the transmission case, a higher position must be prepared formounting of the hydraulic power unit. This arrangement poses a problemof increasing an vehicle height. Since a driving seat is above thehydraulic power unit in a general arrangement, this invites a difficultyfor a driver to get on and off the seat.

As described above, the power transmission path for working unit of theconventional transmission is entirely located in the upper space of thetransmission case. On the other hand, a mid-PTO shaft for driving amid-mount more or the like is located in the lower space of thetransmission case. Accordingly, a power transmission mechanism betweenthe PTO input shaft and the mid-PTO shaft in the conventionaltransmission must be formed throughout the entire region of thetransmission case along the vertical direction. This poses a problem ofnecessitating a complicated structure for the transmission mechanism.

The present invention was conceived in light of those conventionaltechniques. It is an object of the present invention to provide atransmission with the power transmission path for working unit and therunning power transmission path, which is capable of achievingdownsizing of the transmission case, as well as effectively securing aspace for accommodating parts for the hydraulic lift unit or the likewithin the transmission case.

It is another object of the present invention to provide a powertransmission arrangement in a vehicle provided with a working unitoperable by a hydraulic power unit, which is capable of shortening ahydraulic fluid distribution path to the hydraulic power unit.

It is still another object of the present invention to provide a powertransmission arrangement in a vehicle provided with a working unitoperable by a hydraulic power unit, which is capable of stablysupporting a cylinder tube of the hydraulic power unit at a lowerposition.

SUMMARY OF THE INVENTION

To achieve the above objects, there is provided a transmission for aworking vehicle, which includes:

a transmission case providing an accommodation space therein foraccommodating a differential gear unit as locating the samesubstantially below a lengthwise center of the transmission case, inwhich driving power with its speed changed from an engine is divided andtransmitted right and left driving axles through the differential gearunit;

a PTO input shaft supported by the transmission case for receiving thedriving power from the engine;

a running power input shaft supported by the transmission case forreceiving the driving power from the engine via a transmission unit;

the PTO input shaft located with its rotational axis extending in avehicle lengthwise direction substantially at a widthwise center of thetransmission case along a vehicle width direction;

the running power input shaft located with its rotational axis extendingin the vehicle lengthwise direction substantially at the same positionas that of the PTO input shaft along the vehicle width direction and ata lower side of the PTO input shaft; and wherein

the accommodation space for accommodating the differential gear unit isdisplaced to a first lateral side of the vehicle along the vehicle widthdirection, a running power transmission shaft is located on the frontside of the space with its axis extending in the vehicle lengthwisedirection, and the running power input shaft, the running powertransmission shaft and the differential gear unit are interlocked toeach other via a running power gear train;

a mid-PTO shaft having a front end protruding forwards through thetransmission case, the mid-PTO shaft located within the transmissioncase closer to a second lateral side of the transmission case along thevehicle width direction and lower side of the transmission case with itsaxis extending in the vehicle lengthwise direction and its rear endreaching to a rear side of the transmission case;

a PTO power transmission shaft interlocked with the PTO input shaft viaa main PTO gear train located on the front side of the transmissioncase, the PTO power transmission shaft located within the transmissioncase closer to the second lateral side along the vehicle width directionwith its axis extending in the vehicle lengthwise direction and its rearend reaching to the rear side of the transmission case; and

a mid-PTO gear train located within the transmission case closer to arear side thereof for interlocking the PTO power transmission shaft withthe mid-PTO power transmission shaft.

With the transmission having the above arrangement, it is possible toprevent increase in size of the transmission case, while providingwithin the transmission case a free space on the upper side of a runningpower transmission path. This free space may be utilized for example toaccommodate constitutional parts of a hydraulic lift unit.

In addition, since the mid-PTO gear train is located within thetransmission case closer to the rear side thereof, a distal end of themid-PTO shaft, which is driven through the mid-PTO gear train can bepositioned as close as possible to the driving axle. Accordingly, it ispossible to provide a power transmission mechanism for connectionbetween the mid-PTO shaft and the working unit driven by the mid-PTOshaft with an improved durability and noise prevention arrangement.

In the above arrangement, the PTO power transmission shaft and themid-PTO shaft are displaced to the same lateral side along the vehiclewidth direction within the transmission case so as to position both theshafts as close as possible to each other. This can simplify a powertransmission arrangement between both the shafts.

According to a preferable arrangement, the PTO power transmission shaftand the mid-PTO power transmission shaft are respectively located aboveand below the driving axles.

According to another preferable arrangement, the transmission furtherincludes a rear PTO shaft having a rear end protruding rearwards throughthe transmission case located substantially at the widthwise center ofthe transmission case along the vehicle width direction and above thePTO power transmission shaft; and a rear PTO gear train for interlockingthe PTO power transmission shaft with the rear PTO shaft having at leasta part located closer to the first lateral side of the transmission casealong the vehicle width direction than the PTO power transmission shaftis.

According to a still preferable arrangement, the transmission furtherincludes a switching unit for selectively switching on/off powertransmission from the PTO power transmission shaft to at least one ofthe mid-PTO gear train and the rear PTO gear train.

According to another aspect of the present invention, there is provideda power transmission arrangement in a working vehicle with a workingunit mounted thereto, which includes:

an input shaft supported by a transmission case for receiving drivingpower for driving the working unit from a driving source;

a hydraulic power unit for the working unit and a valve unit forcontrolling feeding and discharging of pressurized fluid for thehydraulic power unit are connected with each other along a vehiclelengthwise direction within the transmission case closer to an upperside thereof or on a top surface of the transmission case, and closer toa first lateral side of the transmission case along the vehicle widthdirection;

a hydraulic pump driven through the input shaft is located closer to asecond lateral side along the vehicle width direction than the hydraulicpower unit and the valve unit are;

a fluid distribution path is arranged so that hydraulic fluid reservedwithin the transmission case is drawn around a lower side of thehydraulic pump and then fed into the hydraulic pump through a suctionport thereof, and

the hydraulic pump has a discharge port connected with a suction port ofthe valve unit.

With the aforesaid power transmission arrangement, it is possible toshorten a hydraulic fluid distribution path to the hydraulic power unit,and hence achieves downsizing of the hydraulic pump, downsizing of thevehicle and improved response rate of the hydraulic power unit.

According to a preferable arrangement, the power transmissionarrangement further includes a filter located within the transmissioncase closer to a lower side thereof and substantially at the sameposition as that of the hydraulic pump with respect to the vehiclelengthwise direction; and the fluid distribution path arranged so thatthe hydraulic fluid reserved within the transmission case is fed intothe suction port of the hydraulic pump through the filter.

According to still another aspect of the present invention, there isprovided a power transmission arrangement in a working vehicle with aworking unit mounted thereto in such a manner as to be verticallymovable through a lift arm, which includes:

an input shaft for receiving driving power for driving the working unitfrom a driving source supported by a transmission case with a firstbulging portion upwardly bulging at a position closer to a first lateralside of the transmission case along a vehicle width direction;

a hydraulic power unit for the working unit including a cylinder tubeextending in a vehicle lengthwise direction, a piston reciprocably andfluid-tightly mounted within the cylinder tube and a supporting shaftoperatively connected with the piston in such a manner as to berotatable around its axis based upon reciprocal movement of the piston,in which the cylinder tube is located within a space defined by thefirst bulging portion, and the supporting shaft is supported by thetransmission case so as to extend along the vehicle width direction andhave at least one of first and second ends extending to the outside ofthe transmission case to form an outer extension, with which the liftarm is connected;

a hydraulic pump for feeding pressurized fluid into the hydraulic powerunit located on a top surface of the transmission case closer to asecond lateral side along the vehicle width direction than the firstbulging portion is; and

the input shaft being arranged so that driving power for the hydraulicpump is taken off therethrough.

With the aforesaid power transmission arrangement, it is possible tosupport the cylinder tube at a lower position, thereby lowering thevehicle height and increasing an operational efficiency of the hydraulicpower unit.

According to a preferable arrangement, the transmission case is formedwith a second bulging portion upwardly bulging at a positionsubstantially at the same position as that of the hydraulic pump withrespect to the vehicle width direction, and the hydraulic pump issupported on the second bulging portion.

According to a more preferable arrangement, the power transmissionarrangement further includes at least a drive train extending from theinput shaft to the hydraulic pump so that at least a portion thereof isplaced within a space defined by the second bulging portion.

According to another preferable arrangement, the power transmissionarrangement further includes a valve unit for controlling feeding anddischarging of pressurized fluid for the hydraulic power unit connectedwith the cylinder tube so as to close one of open ends of the cylindertube, the one of open ends being positioned opposite to another side ofthe cylinder tube, on which the supporting shaft is located; and a fluiddistribution path being arranged so that hydraulic fluid reserved withinthe transmission case is drawn around a lower side of the hydraulic pumpand then fed into the hydraulic pump through a suction port thereof. Thehydraulic pump has a discharge port connected with a suction port of thevalve unit.

According to still another preferable arrangement, a filter is locatedwithin the transmission case closer to a lower side thereof andsubstantially at the same position as that of the hydraulic pump alongthe vehicle lengthwise direction; and a fluid distribution path is soarranged that the hydraulic fluid reserved within the transmission caseis fed into the suction port of the hydraulic pump through the filter.

According to another aspect of the present invention, there is provideda transmission for a working vehicle with a working unit mounted theretoin such a manner as to be vertically movable by a hydraulic power unit,which includes:

a transmission case designed to be capable of reserving hydraulic fluidtherein;

a PTO input shaft supported by the transmission case and operativelyconnected with a hydraulic pump so as to operatively receive drivingpower from an engine; and

a running power input shaft supported within the transmission case andoperatively connected with a driving axle so as to operatively receivedriving power from the engine via an HST; wherein

the hydraulic pump is so designed as to feed pressurized fluid to theHST and the hydraulic power unit;

the transmission case includes a front supporting wall and a rearsupporting wall aligned in series along a fore and aft direction of thevehicle to divide an inner space of the transmission case into a frontchamber, a middle chamber and a rear chamber; and

a hydraulic fluid distribution path being so arranged that hydraulicfluid returned from the HST and hydraulic fluid returned from thehydraulic power unit respectively flow into the front chamber and therear chamber, and the hydraulic pump sucks the hydraulic fluid throughthe middle chamber.

With the above relatively simple arrangement, it is possible toeffectively prevent hydraulic fluid, which has been heated to hightemperature during circulation and returned from the HST and thehydraulic power unit, from being fed again to the HST and the hydraulicpower unit before it is cooled. As a result, it is possible toeffectively prevent deterioration in operational efficiency of thehydraulic pump, the HST and the hydraulic power unit.

According to a preferable arrangement, a PTO clutch for switching on/offpower transmission from the PTO input shaft on a downstream side of thehydraulic pump along its power transmission path is placed within thefront chamber, while a drive train for driving the PTO shaft is placedwithin the rear chamber. The front chamber is communicated with the rearchamber through an intermediate chamber, in which a PTO powertransmission shaft for connection between the PTO clutch and the drivetrain is placed.

According to a more preferable arrangement, the transmission furtherincludes a brake shaft located on an upstream side of the driving axlealong its power transmission path, and a brake mechanism for applyingbraking force to the brake shaft. The brake shaft and the brakemechanism may be placed within the intermediate chamber. Theintermediate chamber is designed to enable hydraulic fluid to flowthereinto from the front chamber and then flow out into the middlechamber. More preferably, the rear chamber is provided with an interiorwall for temporarily receiving return fluid from the hydraulic powerunit.

According to a still preferable arrangement, the transmission furtherincludes a mechanical transmission unit for stepwisely varying the speedof driving power inputted to the running power input shaft andoperatively transmitting the driving power to a driving axle. Themechanical transmission may be placed within the front chamber. An inputend of the driving axle is placed within the middle chamber.

According to still another aspect of the present invention, there isprovided a transmission for a working vehicle, which includes:

a transmission case that includes a body with its at least one sidecloser to a first lateral side of the transmission case along a vehiclewidth direction forming a lateral opening and a side cover for closingthe lateral opening, a PTO input shaft supported by the transmissioncase and operatively connected with an engine, a PTO shaft supported bythe transmission case so as to be able to output driving power to theoutside of the transmission case, and a PTO power transmission mechanismconstituting a driving power transmission path between the PTO inputshaft and the PTO shaft, in which:

the PTO power transmission mechanism includes a clutch unit equippedwith a hydraulic clutch mechanism capable of selectively transmitting orshutting off the driving power transmission path between the PTO inputshaft and the PTO shaft;

the clutch unit includes a hydraulic brake mechanism for applyingbraking force to a rotational member of the PTO power transmissionmechanism during shutting-off of the power transmission path by thehydraulic clutch unit;

the hydraulic brake mechanism includes a pressing member having aproximal end slidably fitted in a cylinder chamber and a distal endadapted to be brought into and released from engaging relationship withthe rotational member of the PTO power transmission mechanism, so thatthe pressing member selectively applies braking force to and release thesame from the PTO power transmission mechanism by controlling feeding ofpressurized fluid to the cylinder chamber; and

the cylinder chamber is formed in the side cover of the transmissioncase.

With the above arrangement, the cylinder chamber, which must be fluidtightly sealed, is not formed in the body of the transmission case butin the side cover, thereby omitting the necessity to work the body ofthe transmission with higher precision and therefore enabling the bodyto be relatively easily formed by casting.

According to a preferable arrangement, the hydraulic clutch mechanismand the hydraulic brake mechanism are actuated by working fluid fed froma common hydraulic pressure source. The side cover is provided with aworking-fluid controlling member for controlling feeding of workingfluid to the hydraulic clutch mechanism and the hydraulic brakemechanism and a pressurized-fluid distributor for distributingpressurized fluid into the hydraulic clutch mechanism and the hydraulicbrake mechanism.

According to a more preferable arrangement, the working-fluidcontrolling member and the pressurized-fluid distributor arerespectively and detachably attached on outer and inner surfaces of theside cover.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, and other objects, features and advantages of the presentinvention will become apparent from the detailed description thereof inconjunction with the accompanying drawings wherein.

FIG. 1 is a model view illustrating a lateral side of a vehicle to whichone embodiment of a power transmission arrangement of the presentinvention is applied.

FIG. 2 is a partly exploded perspective view of an HST and atransmission in the power transmission arrangement according to the oneembodiment of the present invention.

FIG. 3 is a longitudinal cross-section of the HST and the transmissionillustrated in FIG. 2.

FIG. 4 is a partially cross-sectioned plan view of the HST and thetransmission illustrated in FIG. 3.

FIG. 5 is a cross-section taken along lines V—V in FIG. 3.

FIG. 6 is a front view of the transmission with a front cover removed.

FIG. 7 is a rear view of the transmission with a rear cover removed

FIG. 8 is a development elevation of a running power drive train of thetransmission taken along lines VIII—VIII in FIG. 6.

FIG. 9 is a development elevation of a PTO drive train of thetransmission taken along lines IX—IX in FIG. 7.

FIG. 10 are partially cross-sectioned plan views of a peripheral portionof a brake shaft in the transmission. Specifically, FIGS. 10( a) and10(b) respectively illustrate states with a differential-lockingmechanism actuated in association with an actuated running brake unitand separately and independently actuated.

FIG. 11 is a cross section taken along lines XI—XI in FIG. 3.

FIG. 12 is a hydraulic circuit diagram of a hydraulic lift unit and avalve unit.

FIG. 13 is a hydraulic circuit diagram of a center section and a PTOclutch unit.

FIG. 14 is a longitudinal cross-section of the center section.

FIG. 15 is a front view of a transmission case with the center sectionremoved.

FIG. 16 is a partially cross-sectioned plan view of a modifiedembodiment of the transmission.

FIG. 17 is a partially cross-sectioned plan view of a modifiedtransmission with a double-headed pump.

FIG. 18 is a hydraulic circuit diagram of the hydraulic lift unit andthe valve unit where the transmission is equipped with double-headedpump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be hereinafterdescribed with reference to the drawings attached hereto. FIG. 1 is amodel view illustrating a lateral side of vehicle 100 to which thisembodiment is applied.

As illustrated in FIG. 1, the vehicle 100 is designed to mount workingunits such as bucket unit 111, mower unit 112 and cultivating unit (notshown) on the front side, lower side of a lengthwise center and rearside of the vehicle. Hereinafter, a working unit such as the mower 112disposed just on the front side of transmission 30 will be referred toas a first working unit, while a working unit such as the cultivatingunit disposed on the rear side of the transmission 30 is referred to asa second working unit.

The vehicle 100 has chassis 101 on which engine 10 a, HST 20 andtransmission 30 disposed in sequence along a vehicle lengthwisedirection, and seat 102 disposed above the transmission 30.

Specifically, power output from the engine 10 a is introduced into inputshaft 21 a of the HST 20 through an elastic joint (not shown) attachedto a rotational center of flywheel 10 b, and power transmission shaft 10c provided with universal joints at the opposite ends and tilteddownwards towards the rear side of the vehicle.

Reference code 10 d in FIG. 1 represents a cooling fan installed on oneof the universal joints of the power transmission shaft 10 c on itsdownstream side with respect to the power transmission path. Air streamsgenerated by the cooling fan 10 d are blown on the HST 20, transmissioncase 60 and the like to indirectly cool hydraulic fluid reserved withinthese members for circulation to respective parts. The cooling fan 10 bis also designed to cool a hereinafter described line filter 68,auxiliary pump 420 and the like.

On the front upper side of the chassis 101 are mounted the engine 10 a,and a radiator and a fuel tank related to the engine 10 a. These arecovered with a bonnet.

On the front lower side of the chassis 101 is supported front axle case10 e extending along a widthwise direction of the chassis. Specifically,the front axle case 10 e is supported by a center pin, which is disposedat substantially the widthwise center of the chassis along the vehiclelengthwise direction, so that opposite ends of the front axle case 10 eare vertically swingable. A front axle extends outwards through theopposite ends of the front axle case 10 e to have outer extensions onwhich front wheels are fitted.

Reference code 10 f in FIG. 1 represents a power transmission shaft forconnection between a hereinafter-describedfront-wheel-driving-power-take-off shaft 53 a, which protrudes forwardlythrough the transmission case 60, and an input shaft of the front axlecase 10 e. The power transmission shaft 10 f includes a substantiallyhorizontally extending first part that has a rear end connected with thefront-wheel-driving-power-take-off shaft 53 a via a universal joint, anda second part that is tilted downwards towards the front side of thevehicle, and has a rear end connected with a front end of the first partvia a universal joint and a front end connected with the input shaft ofthe front axle case via a universal joint. The front wheels are drivenby rotational power synchronized with rear wheels 180.

The seat 102 is mounted on mount stay 10 g installed over a top surfaceof a rear portion of the transmission case 60 and a front surface of ahereinafter-described valve unit 410.

FIG. 2 is a partly exploded perspective view of the HST 20 and thetransmission 30 in the power transmission arrangement of the aforesaidvehicle. FIGS. 3 and 4 are respectively a longitudinal cross-section anda partially cross-sectioned plan view of the HST 20 and the transmission30. FIG. 5 is a cross-section taken along lines V—V in FIG. 3.

As illustrated in FIGS. 2 and 3, the HST 20 includes hydraulic pump body21 having pump shaft 21 a that is operatively connected with the engine10 and disposed along the vehicle lengthwise direction, hydraulic motorbody 22 that has motor shaft 22 a disposed below the pump shaft 21 a inparallel relationship therewith, center section 23 for supporting thehydraulic pump body 21 and the hydraulic motor body 22, and HST casing24 connected with the center section 23 as enclosing the hydraulic pumpbody 21 and the hydraulic motor body 22.

The HST 20 is of a variable displacement type that enables at least oneof the hydraulic pump body 21 and the hydraulic motor body 22 to varythe input/output flow rate based upon external operation, therebyvarying the rotational number of the motor shaft 22 a with respect tothe pump shaft 21 a. Specifically, the HST 20 includes output controlarm 25 for controlling rotational output of the motor shaft 22 a. Theoutput control arm 25 a is operatively connected with a throttle pedalfor forward and rearward travel of the vehicle, which is disposed abovea right step (not shown) installed on the chassis 101.

As illustrated in FIG. 3, rear ends of the pump shaft 21 a and the motorshaft 22 a extend through the center section 23 to have rear extensionsadapted to be respectively connected with a hereinafter-described inputshaft 31 for working unit (PTO input shaft) and input shaft 34 forrunning the vehicle (running power input shaft).

FIGS. 6 and 7 are respectively front and rear views of the transmissionwith front cover 62 and rear cover 63 of the hereinafter-describedtransmission case 60 removed. FIG. 8 is a development elevation of arunning power drive train of the transmission taken along linesVIII—VIII in FIG. 6. FIG. 9 is a development elevation of aworking-vehicle (PTO) drive train of the transmission 30 taken alonglines IX—IX in FIG. 7.

As illustrated in FIGS. 3 to 9, the transmission 30 includesworking-unit driving power input shaft (PTO input shaft) 31 that isdisposed coaxial with the pump shaft 21 a and connected therewith insuch a manner as to be relatively non-rotatable around the axis, rearPTO shaft 32 for the second working unit, mid-PTO shaft 33 for the firstworking unit, PTO power transmission mechanism 40 for connecting the PTOinput shaft 31 with the rear PTO shaft 32 and the mid-PTO shaft 33,running power input shaft 34 that is disposed coaxial with the motorshaft 22 a and connected therewith in such a manner as to be relativelynon-rotatable around the axis, running power transmission mechanism 50for connection between the running power input shaft 34 and ring gear151 of differential gear unit 150 that differentially drives a pair ofdriving wheels, and the transmission case 60 for supporting therespective members.

As illustrated in FIGS. 3, 5, 8 and 9, the transmission case 60 includesbody 61 that forms front and rear openings along the vehicle lengthwisedirection and a lateral opening closer to the first lateral side of thevehicle along the vehicle width direction, the front cover 62 and therear cover 63 for respectively closing the front and rear openings ofthe body 61, and side cover 64 for closing the lateral opening of thebody 61. The thus arranged transmission case 60 is designed to becapable of storing hydraulic fluid in its inner space.

On the rear side of the transmission case 60 is provided working-unitmounting hitch 480 for vertically movably supporting the second workingunit. The working-unit mounting hitch 480 is a three-point link hitchthat includes right and left lower links 482 pivotably supported onright and left mounting stays 481 mounted on the rear side of thetransmission case 60, lift rods 483 that respectively have front endspivotably connected with free ends of hereinafter-described lift arms406 and rear ends pivotably connected with the lower links 482, toplinks 485 that respectively have front ends pivotably supported onmounting bracket 484 mounted to a rear surface of an upper portion ofthe rear cover 63 (see FIGS. 2 and 3).

The body 61 has front supporting wall 61 a and rear supporting wall 61 brespectively closer to the front and rear sides along the vehiclelengthwise direction, as best shown in FIG. 3.

The front supporting wall 61 a and the rear supporting wall 61 bdisposed in sequence along the fore and aft direction of the vehicledivide an inner space of the body 61 into front chamber C1, middlechamber C2 and rear chamber C3. These front, middle and rear chambersC1, C2, C3 are arranged to allow the circulation of hydraulic fluidtherethrough.

In this embodiment, intermediate chamber C4 is additionally providedabove the middle chamber C2, so that hydraulic fluid is circulatedbetween the front, middle, rear and intermediate chambers C1, C2, C3,C4.

Specifically, fluid communication opening 61x for communication betweenthe front chamber C1 and the intermediate chamber C4 is providedsubstantially at a vertical center of the front supporting wall. Theintermediate chamber C4 opens to the rear chamber C3 through an openingformed in the rear supporting wall 61 b. At a vertically lower portionof the rear supporting wall 61 b is formed fluid communication opening61 y for communication between the middle chamber C2 and the rearchamber C3 (see FIGS. 3, 7 and 9).

On the lower side of the middle chamber C2 is secured a space foraccommodation of a power transmission mechanism for transmitting drivingpower to the driving axle. Specifically, an input end (inner end) of thedriving axle is supported at a portion below the middle chamber C2. Inthis embodiment, the differential gear unit is provided as the drivingpower transmission mechanism to the driving axle. Accordingly, a spacefor accommodation of the differential gear unit is secured on the lowerside of the middle chamber C2.

More specifically, as illustrated in FIG. 5, the accommodation space asmentioned above is displaced closer to the first lateral side of thetransmission case along the vehicle width direction than the runningpower input shaft 34, which will be hereinafter described in detail.

In FIG. 6, reference code OL represents a fluid level of hydraulic fluidthat has been reserved to a predetermined amount by pouring through ahereinafter-described fluid feeding plug 62 d. This fluid level is setto be slightly higher than the height of the fluid communication opening61 x. More specifically, the front, middle, rear and intermediatechambers C1, C2, C3, C4 have the fluid level OL as illustrated beforestarting the engine. On the contrary, after starting the engine, thefluid level OL of the front chamber C1, to which drain fluid caused bythe operation of the HST accompanied is flown, tends to increase, whilethe fluid level OL of the middle chamber C2 from which reservoir fluidis sucked out by the auxiliary hydraulic pump 420, tends to decrease.

Reference code 61 x′ in FIGS. 6 and 8 represents a fluid communicationopening formed on the lower side of the front supporting wall 61 a forcommunication between a lower portion of the front chamber C1 and themiddle chamber C2. The fluid communication opening 61 x′ is not designedto allow positive fluid flow from the front chamber C1 to the middlechamber C2, but to prevent hydraulic fluid from staying in the frontchamber C1 when hydraulic fluid is removed from the transmission case.Therefore, the fluid communication opening 61 x′ has a minimized size.

The front supporting wall 61 a is designed to support the rear ends ofthe PTO input shaft 31 and the running power input shaft 34substantially at the widthwise center of the transmission case 60.Specifically, both the PTO input shaft 31 and the running power inputshaft 34 are supported by the front cover 62 and the front supportingwall 61 a along substantially the widthwise center line of thetransmission case in vertically spaced and parallel relationship.

More specifically, as best illustrated in FIGS. 2, 3 and 6, the PTOinput shaft 31 has a front end supported by the front cover 62 in such amanner as to be connectable with the pump shaft and a rear end supportedby the front supporting wall 61 a, so that the rotational axis of thePTO input shaft 31 extends along the vehicle lengthwise direction atsubstantially the widthwise center of the transmission case 60.

On the other hand, the running power input shaft 34 has a front endsupported by the front cover 62 in such a manner as to be connectablewith the motor shaft, and a rear end supported by the front supportingwall 61 a, so that the rotational axis of the running power input shaft34 extends along the vehicle lengthwise direction at the widthwisecenter of the transmission case 60 on the lower side of the PTO inputshaft 31.

The rear supporting wall 61 b is designed to support a front end of therear PTO shaft 32. Specifically, the rear PTO shaft 32 is supported bythe rear supporting wall 61 b and the rear cover 63. More specifically,the rear PTO shaft 32 is supported by the rear supporting wall 61 b andthe rear cover 63 so that the rotational axis of the rear PTO shaft 32extends along the vehicle lengthwise direction and has a rear endprotruding rearwards through the rear cover 63.

The front cover 62 is connected with the body 61 so as to cover thefront opening of the body 61 and support the center section 23. That is,the center section 23 is connected with the front cover as supportingthe hydraulic pump body 21 and the hydraulic motor body 22.

In this embodiment, the front cover 62 is provided to close the frontopening of the body 61. Alternatively, the center section 23 may bedesigned to close the front opening of the body 61.

The mid-PTO shaft 33 acts as a driving shaft of the first working unit112 such as a mower unit disposed below the lengthwise center of thechassis 101. Therefore, the mid-PTO shaft 33 is supported by the frontsupporting wall 61 a and the rear supporting wall 61 b within thetransmission case 60 closer to the lower side thereof in such a manneras to have a rotational axis extending in the vehicle lengthwisedirection and a front end protruding forwards through the transmissioncase 60.

Input shaft 112 of the first working unit 112 operatively connected withthe mid-PTO shaft 33 (see FIG. 1) is preferably displaced from thewidthwise center of the vehicle to the first or second lateral sidealong the vehicle width direction so as to minimize increase of thevehicle height and prevent interference with the chassis 101. In thisembodiment, as described above, the differential gear unit 150 isaccommodated within the transmission case 60 closer to the first lateralside and lower side thereof. Accordingly, it is preferable to displacealong the vehicle width direction the input shaft 112 of the firstworking unit 112 to the second lateral side, which is opposite to thefirst lateral side with the differential gear unit 150 displacedthereto, while displacing the mid-PTO shaft 33 to the second lateralside. With this arrangement, it is possible to limit increase of thevehicle height and prevent interference with the differential gear unit150, as well as simplifying the power transmission mechanism forconnection between the mid-PTO shaft 33 and the input shaft 112 of thefirst working unit 112.

In this embodiment, as illustrated in FIG. 3, for positioning themid-PTO shaft 33 as close as possible to a ground, the mid-PTO shaft 33is located on the lower side of a pair of the driving axles 180. Thisarrangement enables a simplified structure of the power transmission forconnection between the mid-PTO shaft 33 and the first working unit 112.

That is, the first working unit 112 is designed to take an operationposition where it is placed on the ground and a standby position whereit has been elevated from the ground. For achieving these positions, thefirst working unit 112 is connected with the mid-PTO shaft 33 via thepower transmission mechanism equipped with universal joints. In thiscase, if the mid-PTO shaft 33 is located as close as possible to theground, a bending angle of the universal joints to the PTO shaft 33 whenthe first working unit 112 has been brought into the operationalposition can be minimized, thereby achieving a simplified structure ofthe power transmission mechanism with the universal joints.

In FIG. 1, reference code 112′ represents a front PTO unit. In thisembodiment, the front PTO unit 112′ is detachably hooked on a bottomsurface of the front axle 10 e. The front PTO unit 112′ is used for aworking unit such as a snow removing unit to be mounted on the frontside of the vehicle, as an alternative to the arrangement with the firstworking unit 112 such as the mower mounted on the lower side of thevehicle as mentioned above. Specifically, the front PTO shaft, whichextends along the vehicle lengthwise direction, has a rear end connectedwith the mid-PTO shaft 33 via a shaft coupling, and a front endconnected with a driving part of the working unit via a shaft coupling.

The PTO power transmission mechanism 40 includes, as best shown in FIGS.3, 6, 7 and 9, PTO power transmission shaft 41 extends along the vehiclelengthwise direction and is supported within the transmission case 60 asstraddling between the intermediate chamber C4 and the rear chamber C3,PTO clutch unit 70 for switching on/off power transmission from the PTOinput shaft 31 to the PTO power transmission shaft 41, PTO gear train 42for connection between the PTO power transmission shaft. 41 and the rearPTO shaft 32, mid-PTO power transmission gear train 43 for connectionbetween the PTO power transmission shaft 41 and the mid-PTO shaft 33,and switching unit 45 for switching on/off power transmission from thePTO power transmission shaft 41 to the rear PTO gear train 42 and/or themid-PTO power transmission gear train 43.

The PTO power transmission shaft 41 is, as best illustrated in FIGS. 6and 9, supported by the front supporting wall 61 a and the rear cover 63in such a manner as to have a rotational axis extending along thevehicle lengthwise direction and located closer to the second lateralside of the transmission case 60 than the PTO input shaft 31, which sideis the opposite side to the first lateral side with the differentialgear unit accommodation space displaced thereto, and a rear end reachingthe rear side of the transmission case 60.

The PTO power transmission shaft 41 acts as a driving shaft for themid-PTO shaft 33 and the rear PTO shaft 32. As described above, themid-PTO shaft 33 is located within the transmission case 60 closer tothe lower side thereof, while the rear PTO shaft 32 is located withinthe transmission case 60 closer to the upper side thereof. Accordingly,in this embodiment, as illustrated in FIG. 6, the PTO power transmissionshaft 41 is located lower than the PTO input shaft 31, so that drivingpower from the PTO power transmission shaft 41 to both the mid-PTO shaft33 and the rear PTO shaft 32 can be efficiently transmitted with arelatively simple arrangement.

As illustrated in FIG. 9, the PTO clutch unit 70 is located within thefront chamber C1 of the transmission case 60. That is, in thisembodiment, the switching on/off driving power to be transmitted fromthe PTO input shaft 31 to the PTO power transmission shaft 41 is madewithin the transmission case 60 closer to the front side thereof.

Specifically, the PTO clutch unit 70 includes driving-side member 71relatively non-rotatably and axially non-slidably supported on the PTOinput shaft 31, driving-side friction plate 72 supported on thedriving-side member 71, driven-side member 73 relatively rotatablysupported on the PTO input shaft 31, driven-side friction plate 74relatively non-rotatably and axially slidably supported on thedriven-side member 73, clutch pressing member 75 for bringing thedriven-side friction plate 74 into frictional engagement with thedriving-side friction plate 72 upon receiving hydraulic pressure, clutchbiasing member 76 for moving the clutch pressing member 75 away from thedriving-side friction plate 72 and the driven-side friction plate 74,and PTO power transmission gear 77 relatively non-rotatably supported ona front end of the PTO power transmission shaft 41 in meshed engagementwith the driven-side member 73.

The PTO clutch unit 70 of the above arrangement acts as a main PTO geartrain for transmitting driving power from the PTO input shaft 31 to thePTO power transmission shaft 41 via the driven-side member 73 where theclutch pressing member 75 has brought both the friction plates 72, 74into frictional engagement with each other upon receiving hydraulicpressure, and acts as a shut-off member for shutting off the powertransmission from the PTO input shaft 31 to the driven-side member 73where it is not subjected to hydraulic pressure.

In this embodiment, the PTO clutch unit 70 further includes PTO brakemechanism 80 that is operable in association with clutching motion ofthe PTO clutch unit 70. Accordingly, this PTO brake mechanism 80effectively prevents free rotation of the rear PTO shaft 32 and themid-PTO shaft 33 due to inertia force of the connected working unit inthe wake of shutting off the power by the PTO clutch unit 70.

The PTO brake mechanism 80 includes brake disc 81 relativelynon-rotatably mounted on the driven-side member 73 (i.e., an outerperiphery of the driven-side member 73 in this embodiment), brake shoe82 located so as to be frictionally engageable with the brake disc 81,brake pressing member 83 having a distal end supporting the brake shoe82 and a proximal end axially slidably supported on cylinder chamber 85formed in the transmission case 60, and brake biasing member 84 forbiasing the brake pressing member 83 so as to bring the brake shoe 82into frictional engagement with the brake disc 81. With thisarrangement, where the brake pressing member 83 is not subjected tohydraulic pressure, the brake shoe 82 is brought into frictionalengagement with the brake disc 81 upon receiving biasing force effectedby the brake biasing member 84, thereby applying braking force to thebrake disc 81. On the other hand, where the brake pressing member 83 issubjected to hydraulic pressure, the brake pressing member 83 is movedin a direction away from the brake shoe 82 against the biasing force ofthe brake biasing member 84, thereby applying no braking force to thebrake disc 81.

More preferably, the cylinder chamber 85 is formed in the side cover 64.The reason for forming the cylinder chamber 85, which must be tightlysealed, not in the body 61 but the side cover 64 is that there will beno need to form the body 61 with an increased precision and thereforethe body 61 can be relatively easily formed by casting.

Operations of applying hydraulic pressure to the brake pressing member83 and the clutch pressing member 75 respectively are associated witheach other. That is, where the clutch unit 70 is brought into the ONstate by the application of hydraulic pressure to the clutch pressingmember 75, hydraulic pressure is also applied to the brake pressingmember 83, thereby bringing the brake mechanism 80 into the OFF state.On the other hand, where the clutch unit 70 is brought into the OFFstate by the application of no hydraulic pressure to the clutch pressingmember 75, hydraulic pressure is also not applied to the brake pressingmember 83, thereby bringing the brake mechanism 80 into the ON state.That is, the hydraulic brake mechanism 80 and the hydraulic clutch unit70 are controlled by a common hydraulic source so as to be operated inassociation with each other.

In this embodiment, PTO line 602, which receives pressurized fluid fromthe hereinafter described auxiliary hydraulic pump 420, is used as thecommon hydraulic source for the hydraulic brake mechanism 80 and thehydraulic clutch unit 70. More specifically, valve assembly 650, whichis equipped with switch valve 604 for controlling feeding of workingfluid from the PTO line 620 to the hydraulic brake mechanism 80 and thehydraulic clutch unit 70, is fixedly attached on an outer surface of theside cover 64.

On the inner surface of the side cover 64 is provided apressurized-fluid distributor for distributing pressurized fluid of thePTO line 602 into the hydraulic brake mechanism 80 and the hydraulicclutch unit 70.

In this embodiment, the side cover 64 forms therein hole 615 having anouter end communicated with the PTO line 602 and an inner end openingthrough an inner surface of the side cover 64. Also, as thepressurized-fluid distributor, there is provided manifold 616 havingfirst end 616 a communicated with the inner end of the hole 615 andsecond end in the form of first and second open ends 616 b, 616 crespectively facing the clutch pressing member 75 and the brake pressingmember 83. The first open end 616 b and the second open end 616 crespectively constitute hereinafter-described clutch line 611 and brakeline 612.

In this embodiment, as illustrated in FIG. 3, the first open end 616 bfaces in the vehicle width direction, and the second open end 616 cfaces in the vehicle lengthwise direction. Preferably, at least one ofthe first open end 616 b and the second open end 616 c may be formed bya pipe or any other separable members, thereby achieving improvedworkability and fabricability of the manifold.

In this embodiment, the brake mechanism 80 is provided with accumulatormechanism 80 a for absorbing shift shocks caused by shifting the PTOclutch unit 70 from the power shut-off state to the power transmissionstate (see FIG. 13).

Specifically, the brake pressing member 83 includes rod 83 a having aproximal end positioned within the cylinder chamber 85 and a distal endwith the brake shoe 82 mounted thereon, pressure receiving plate 83 bthat is axially slidably supported on the rod 83 a so as to drive thecylinder chamber 85 into pressurized-fluid operation chamber 85 a andbiasing-member accommodation chamber 85 b, and driven plate 83 c axiallynon-movably supported on the rod 83 a so as to be positioned within thebiasing-member accommodation chamber 85 b.

The pressure receiving member 83 b forms therein orifice 85 b′ forcommunication between the pressurized-fluid operation chamber 85 a andthe biasing-member accommodation chamber 85 b. The orifice 85 b′ isadapted to be closed by the driven plate 83 c when the pressurereceiving plate 85 b is pressed towards the biasing-member accommodationchamber 85 b by a predetermined stroke upon receiving hydraulicpressure.

The PTO brake mechanism 80 having the above arrangement is operated inthe manner as described below.

When pressurized fluid is fed through the PTO line 602, hydraulicpressures in the clutch line 611 and the brake line 612 increase, whichcauses pressurized fluid to leak out through the orifice 85 b′.Accordingly, the hydraulic pressures in the clutch line 611 and thebrake line 612 gradually increase at the initial stage, so that thehydraulic clutch unit 70 is gradually brought into the engaged state.Then, the pressure receiving plate 85 b is pressed by pressurized fluid,and then the orifice 85 b′ is closed. Hence, the hydraulic pressures inthe clutch line 611 and the brake line 612 increase to predeterminedvalues.

Thus, in this embodiment, the hydraulic pressure in the clutch line 611can be gradually increased until the orifice 85 b′ is closed by thepressure receiving plate 85 b that has been pressed by a predeterminedstroke. Therefore, it is possible to prevent abrupt engagement of thehydraulic clutch unit 70 and hence effectively prevent wear-out/damagesof the respective members.

As illustrated in FIG. 9, the rear PTO gear train 42 is accommodatedwithin the rear chamber C3 of the transmission case 60. Morespecifically, the rear PTO gear train 42 includes rear-PTO gear member42 a relatively rotatably supported on a portion of the PTO powertransmission shaft 41 in proximity to the rear end thereof, idle gear 42b meshed with the gear member 42 a, intermediate shaft 42 c relativelynon-rotatably supporting the idle gear 42 b, and final gear 42 erelatively non-rotatably supported on the rear PTO shaft 32 in proximityto the front end thereof so as to be meshed with spline 42 d provided onthe intermediate shaft 42 c.

As best illustrated in FIG. 9, the mid-PTO power transmission gear train43 is located on the rear side of the pair of driving axles 180. Thatis, the mid-PTO power transmission gear train 43 is arranged within therear chamber C3 so as to be located on the rear side of the differentialgear unit 150, thereby preventing interference with the differentialgear unit 150 located lower than the middle chamber C2 within thetransmission case 60.

Specifically, the mid-PTO power transmission gear train 43 includesmid-PTO gear member 43 a relatively rotatably supported on the PTO powertransmission shaft 41 with facing the rear-PTO gear member 42 a, idlegear 43 b meshed with the gear member 43 a, and final gear 43 crelatively non-rotatably supported on a rear end of the mid-PTO shaft 33in meshed engagement with the idle gear 43 b.

The switching unit 45 is so designed as to be capable of transmittingrotational force of the PTO power transmission shaft 41 to the rear-PTOgear member 42 a and/or the mid-PTO gear member 43 a by the externaloperation.

Specifically, the rear-PTO gear member 42 a and the mid-PTO gear member43 a respectively have engagement elements 42 a′, 43 a′ disposed in aface-to-face relationship with each other. The switching unit 45includes spline hub 45 a relatively non-rotatably supported on the PTOpower transmission shaft 41 so as to be positioned between theengagement elements 42 a′, 43 a′ of the rear PTO gear member 42 a andthe mid-PTO gear member 43 a, clutch shifter 45 b axially slidably andrelatively non-rotatably fitted on the spline hub 45 a as straddling thespline hub 45 a and the engagement element 42 a′ of the rear-PTO gearmember 42 a and/or the engagement element 43 a′ of the mid-PTO gearmember 43 a, and arm 45 c (see FIG. 7) for operating the clutch shifter45 b.

As described above, the clutch shifter 45 b is relatively non-rotatablyand axially movably fitted on the spline hub 45 a and the engagementelements 42 a′, 43 a′ of the rear PTO gear member and the mid-PTO gearmember. The thus arranged clutch shifter 45 b is designed to be capableof selectively taking a rear-PTO output position enabling the spline hub45 a to be relatively non-rotatably connected with the rear-PTO gearmember 42 a according to its axial position, a mid-PTO output positionenabling the spline hub 45 a to be relatively non-rotatably connectedwith the mid-PTO gear member 43 a, and a rear- and mid-PTO outputposition enabling the spline hub 45 a to be relatively non-rotatablyconnected with both the rear PTO gear member 42 a and the mid-PTO gearmember 43 a.

As best illustrated in FIGS. 3, 5, 6 and 8, the running powertransmission mechanism 50 includes speed-change shaft (running powertransmission shaft) 51 supported within the transmission case 60 so asto be located closer to the first lateral side of the transmission case60 than the running power input shaft 34 in a laterally adjacentrelationship with each other along the vehicle width direction and havea rotational axis extending along the vehicle lengthwise direction,mechanical transmission unit 52 for transmitting/shutting off the powerwith its speed stepwisely changed between the running power input shaft34 and the running power transmission shaft 51, optionalfront-wheel-driving-power-take-off unit 53, and travelling brake unit200 interposed between the speed-change shaft 51 and ring gear 151 ofthe differential gear unit 150.

The running power transmission shaft 51 is located on the front side ofthe differential gear unit 150 located closer to the first lateral sideof the transmission case 60. That is, the running power transmissionshaft 51 is located closer to the first lateral side of the transmissioncase 60 than the running power input shaft 34, which is locatedsubstantially at the widthwise center of the transmission case 60, inwhich the first lateral side is the same side as the side to which thedifferential gear unit 150 is displaced.

The mechanical transmission unit 52 includes driving-side gear 52 arelatively non-rotatably supported on the running power input shaft 34,driven-side member 52 b having plural driven-side gears (two in thisembodiment) selectively capable of meshing with the driving-side gear 52a and relatively non-rotatably and axially slidably supported on thespeed-change shaft 51, and an operation member (not shown) for movingthe driven-side member 52 b in the axial direction of the speed-changeshaft 51. With this arrangement, by bringing one of the driven-sidegears into meshing engagement with the driving-side gear 52 a, thedriving power with its speed changed can be transmitted from the runningpower input shaft 34 to the running power transmission shaft 51.

The front-wheel-driving-power-take-off unit 53 is located within thetransmission case 60 closer to the front side thereof, and first lateralside and lower side of the transmission case 60 with reference to therunning power transmission shaft 51. That is, thefront-wheel-driving-power-take-off unit 53 is located in thetransmission case 60 closer to the front side, and first lateral sideand lower side of the transmission case 60 than the running power inputshaft 34 and the running power transmission shaft 51 are.

Specifically, the front-wheel-driving-power-take-off unit 53 includesfront-wheel-driving-power-take-off shaft 53 a supported at a positioncloser to the first lateral side and lower side of the transmission case60 so as to have a front end extending forwards through the transmissioncase 60, and gear train 53 b with a clutch for connection between therunning power transmission shaft 51 and thefront-wheel-driving-power-take-off shaft 53 a.

The travelling brake unit 200 is designed to be operable by a singlebrake pedal 205 (see FIG. 1) located on a left step provided on thechassis 101. Specifically, as illustrated in FIGS. 3, 5 and 8, thetravelling brake unit 200 includes brake shaft 201 supported within thetransmission case 60 so as to extend along the vehicle width direction,driving-side bevel gear 202 relatively non-rotatably supported on a rearend of the speed-change shaft 51, driven-side bevel gear 203 relativelynon-rotatably supported on the brake shaft 201 in meshed engagement withthe driving-side bevel gear 202, output gear 204 provided on the brakeshaft 201 in meshed engagement with the ring gear 151, and brakemechanism 210 for stopping rotation of the brake shaft 201 based uponthe external operation.

As illustrated in FIG. 8, the brake mechanism 210 includes brake cover218 that is connected with a side surface of the body 61 of thetransmission case 60, which side is closer to the second lateral sidethereof, and that defines the intermediate chamber C4 on the upper sideof the middle chamber C2 in cooperation with the body 51, driving-sidefriction plate 211 relatively non-rotatably and axially slidablysupported on the brake shaft 201, driven-side friction plate 212relatively non-rotatably supported within the transmission case 60 in aface-to-face relationship with the driving-side friction plate 211,ring-shaped pressing member 213 that has pressing surface 213 a facingthe driving-side friction plate 211 and supported axially movably on thebrake shaft 201 and relatively rotatably around the axis of the brakeshaft 201, slanting cam groove 213 c formed in rear surface 213 bopposite to the pressing surface 213 a of the pressing member 213 insuch a manner as to be gradually thickened as it advances towards afirst side along a peripheral direction of the pressing member 231, ball214 located within the slanting cam groove 213 c, ball-holding recess215 formed on an inner surface of the brake cover 218, which surfacefacing the rear surface 213 b of the pressing member 213, for fixedlyholding the ball 214, connection arm 216 that has an inner end connectedwith the pressing member 213 via a cam and an outer end relativelyrotatably supported on the brake cover 218 as extending to the outsideof the transmission case 60 and that is adapted to rotate the pressingmember 213 in the peripheral direction by its rotation on its axis, andoperation member 217 for connection between the outer end of theconnection arm 216 and the brake pedal 205 (see FIG. 1) and rotation ofthe connection arm 216 around its axis based upon the operation of thebrake pedal 205.

The thus arranged brake mechanism 210 is so operated that the ball 214presses the pressing member 212 towards the brake shaft 201 by rotatingthe pressing member 213 to the first side along the peripheral directionthereof through the operation of the operation member 217, therebybringing the driving-side friction plate 211 into frictional engagementwith the driven-side friction plate 212 to stop the rotation of thebrake shaft 201.

Preferably, the pressing member 213 is connected with the brake cover218 in such a manner as to be capable of moving towards the brake cover218 by a braking stroke, while holding the ball 214 in its space to thebrake cover 218.

Specifically, the pressing member 213 includes plate body 213 d formingtherein a center hole extending in the axial direction of the brakeshaft 201, and connection member 213 e of a substantially cylindricalshape fitted within the center hole in elastic engagement with the platebody 213 d.

The connection member 213 e has a proximal end formed with a radiallyoutwardly extending flange portion and a distal end formed with aninwardly threaded portion. The thus formed connection member 213 e isfitted within the center hole of the plate body 213 d with the flangeportion radially inwardly compressed, enabling the connection member 213e to be elastically connected with the plate body 213 d by a resilientforce of the flange portion.

The connection member 213 e of the above arrangement is connected withthe brake cover 218 via threaded member 219, thereby enabling the platebody 213 d to move towards the brake cover 218 in the axial direction ofthe brake shaft 201.

Around an inner periphery of the center hole of the plate body 213 d andcloser to a rear side of the same is provided stopper piece 213 f inspaced apart relationship with an abutting portion of the plate body 213d against the flange portion of the connection member 213 e. The stopperpiece 213 f defines a movable range of the plate body 213 d to the brakecover 218. That is, the distance between an abutting point of the flangeportion within the center hole and the stopper piece 213 f correspondsto the braking stroke.

According to the above arrangement, the brake cover 218 can beincorporated into the body 61 of the transmission case 60 with thepressing member 213 and the brake cover 218 connected to each other withthe ball 214 held therebetween. Therefore, it is possible to achieve animproved efficiency in assembling the brake mechanism 210, whileproducing a sufficient braking capability by the brake mechanism 210.

The running power transmission mechanism 50 is provided withdifferential-locking mechanism 250 for locking the differential gearunit 150. The differential-locking mechanism 250 is designed to becapable of forcibly locking rotation of bevel gears 154 about pivotalshaft 153. These bevel gears 154 move around the pair of the drivingaxles 180 in association with the rotation of the ring gear 151 and arerelatively rotatably supported by the pivotal shaft 153 in meshedengagement with a pair of side bevel gears 152, which are respectivelyand relatively non-rotatably supported on the pair of the driving axles180 (see FIG. 5).

Specifically, as illustrated in FIGS. 5 and 8, the differential-lockingmechanism 250 includes locking member 251 that is designed to be capableof taking a locking position enabling the ring gear 151 to be relativelynon-rotatably engaged with one of the pair of the side bevel gears 152and a releasing position enabling the ring gear 151 to be released fromthe relatively non-rotatable engagement with the one of the pair of theside bevel gears 152, differential-locking fork shaft 252 that isaxially movably supported to the transmission case 60 with its axisextending along the vehicle width direction and is capable of movingalong its axis based upon the operation from the outside of thetransmission case 60, differential-locking fork 253 that has a proximalend axially slidably supported on the differential-locking shaft 252 anda distal end engaged with the locking member 251, a pair of first andsecond return springs 254 a, 254 b supported on the differential-lockingfork shaft 252 with the proximal end of the differential-locking fork253 therebetween, first stopper member 255 a fitted around thedifferential-locking fork shaft 252 in abutting engagement with an outerend of the first return spring 254 a and is capable of moving along withthe differential-locking fork shaft 252 when it moves to one side alongthe axis (locking direction), and second stopper member 255 b that hasan inner end disposed in abutting engagement with an outer end of thesecond return spring 254 b and an outer end fitted around thedifferential-locking fork shaft 252 in abutting engagement with theinner surface of the side cover 64 and is capable of relatively movingthe differential-locking fork shaft 252 along the axis.

The differential-locking mechanism 250 of the above arrangement isoperated in the following manner.

By moving the differential-locking fork shaft 252 to the first sidealong the axis, the first stopper member 255 a compresses the firstreturn spring 254 a. The differential-locking fork 253 then moves ascompressing the second return spring 254 b upon receiving the elasticforce of the first return spring 254 a, thereby moving the lockingmember 251 into the locking position.

Then, by releasing the operational force from the differential-lockingshaft 252, the differential-locking fork 253 and thedifferential-locking fork shaft 252 return to a second side along theaxis (releasing direction) by the biasing force of the second returnspring 254 b, thereby moving the locking member 251 into the releasingposition.

Thus, the differential-locking mechanism 250 is so operated as to lockthe differential gear unit 150 upon the application of the operationalforce to the differential-locking fork shaft 252, and automaticallyrelease the differential gear unit 150 from the locked state uponreleasing the operational force.

The running power transmission mechanism 50 also includes link mechanism300 for simultaneously stopping both the pair of the driving axles 180upon the operation of the travelling brake unit 200. That is, asdescribed above, the travelling brake unit 200 is designed to apply abraking force to the brake shaft 201 located on the upstream side of thedifferential gear unit. Accordingly, where the brake mechanism 200 isoperated without locking the differential gear unit 150, there may causetime difference in stopping the pair of the driving axles 180 due todifference in loads respectively applied to the pair of the drivingaxles 180. This time difference indicates the fact that one drivingwheel keeps on rotating while another driving wheel stops its rotation,thereby causing the vehicle to slide sideways when it is stopped.Therefore, the differential gear unit 150 must be locked when thetravelling brake unit 200 is operated.

On the other hand, where one of the pair of the driving wheels slips inthe mud or the like, the differential gear unit 150 must be locked so asto transmit a sufficient power to another driving wheel. To overcomethis situation, only the differential-locking mechanism 250 must beoperated (locked) without operating the travelling brake unit 200 as amatter of course.

The link mechanism 300 is provided for meeting the above demand, andtherefore designed to be capable of solely operating (locking) thedifferential-locking mechanism 250 as forcibly operating (locking) thedifferential-locking mechanism 250 at the time of operation of thetravelling brake unit 200.

Specifically, as illustrated in FIG. 8, the link mechanism 300 includespivoting member 302 that is pivotably supported on pivot shaft 301 so asto move the differential-locking fork shaft 252 along the axis,differential-locking operation member 303 that has a distal end directlyor indirectly connected with the pivoting member 302, and elongatedconnection member 304 that has a distal end engaged with the pivotingmember 302 and a proximal end engaged with the connection arm 216 of thetravelling brake unit 200, and moves towards the pivoting member 302 inassociation with the rotation of the connection arm 216 in such adirection as to actuate the travelling brake unit 200.

The pivoting member 302 forms therein first and second elongated holes305, 306 extending along a pivoting direction of the pivoting member302. Distal ends of the differential-locking operation member 303 andthe connection member 304 are respectively held within the first andsecond elongated holes 305, 306.

The first elongated hole 305 extends between first end 305 a closer to afirst side of the pivoting direction of the pivoting member 302 andsecond end 305 b closer to a second side of the pivoting direction, inwhich the distal end of the connection member 304 engages the first end305 a enabling the pivoting member 302 to press the differential-lockingfork shaft 252, while the distal end of the connection member 304engages the second end 305 b enabling the pivoting member to move awayfrom the differential-locking fork shaft 252. Similarly, the secondelongated hole 306 extends between first end 306 a and second end 306 brespectively closer to the first and second sides of the pivotingdirection of the pivoting member 302.

FIG. 10 are partially cross-sectioned plan views of a peripheral portionof the brake shaft in the transmission. Specifically, FIGS. 10( a) and10(b) respectively illustrate a state where the travelling brake unit200 is in an operative position and a state where only the differentiallocking unit is in an operative position.

As illustrated in FIG. 8, where both the travelling brake unit 200 andthe differential-locking mechanism 250 are out of the operation, thedistal ends of the differential-locking operation member 303 and theelongated connection member 304 are positioned at the first ends 305 a,306 a of the first and second elongated holes 305, 306 closer to thefirst side of the pivoting direction. Once the travelling brake unit 200is actuated in this state, the connection member 304 is moved towardsthe pivoting member 302, thereby pivoting the pivoting member 302towards the first side of the pivoting direction. Accordingly, thedifferential fork shaft 252 is pressed by the pivoting member 302 (seeFIG. 10( a)).

On the other hand, where only the differential-locking mechanism 250 isoperated in a state as illustrated in FIG. 8, the pivoting member 302 ispivoted towards the first side of the pivoting direction by thedifferential-locking operation member 303, thereby moving thedifferential-locking fork shaft 252, as illustrated in FIG. 10( b),while not moving the connection member 304. That is, although thepivoting member 302 is pivoted towards the first side of the pivotingdirection, the connection member 304 is not moved by the interference ofthe second elongated hole 306.

Thus, the link mechanism 300 is designed to be capable of forciblylocking the differential-locking mechanism 250 in association with theoperation of the travelling brake unit 200, while allowing only thedifferential-locking mechanism 250 to be actuated.

The transmission 30 having the above arrangement can produce thefollowing desirable effects in addition to those described above.

That is, the PTO input shaft 31 and the running power input shaft 34 arealigned in vertically spaced apart relationship with each other atsubstantially the widthwise center of the transmission case 60, whilethe PTO power transmission mechanism 40 following a downstream side ofthe PTO input shaft 31 is located only in a space of the transmissioncase 60 closer to the second lateral side thereof than the PTO inputshaft 31 is, and the running power transmission mechanism 50 following adownstream side of the running power input shaft 34 is located only in aspace of the transmission case 60 closer to the first lateral side andlower side of the transmission case 60 than the running power inputshaft 34 is. As a result, it is possible to effectively shorten thelength along the vehicle lengthwise direction of the transmission case60 and vertical length of the same, while assigning a space above therunning power transmission mechanism 50 as an accommodation space forother members. This accommodation space can be used for example foraccommodating cylinder tube 401 of hydraulic lift unit 400 (hereinafterdescribed) or the like.

Also, the transmission of the driving power from the PTO powertransmission shaft 41 to the mid-PTO shaft 33 is achieved through themid-PTO power transmission gear train 43 located on the rear side of thedifferential gear unit 150. Therefore, an end position (position atwhich the driving power is taken off) can be positioned as close aspossible to the pair of the driving axles 180. This close positioning ofthe end position of the mid-PTO shaft 33 to the pair of the drivingaxles 180 in turn achieves a broader distance between the end of themid-PTO shaft 33 and the first working unit 112 driven by the mid-PTOshaft 33, and hence achieves a smaller bending angle of the universaljoint of the transmission mechanism with respect to the mid-PTO shaft33, which mechanism connecting between the first working unit 112 andthe mid-PTO shaft 33, with the first working unit 112 elevated.Therefore, it is possible to smoothly move the first working unit 112 ina vertical direction, and achieve a desirable result such as reducednoises and improved durability.

In the transmission 30, the PTO power transmission shaft 41 is displacedto the second lateral side of the transmission case 60, as describedabove. Also, the mid-PTO shaft 33 is displaced to the second lateralside of the transmission case 60. Accordingly, a straight distancebetween the PTO power transmission shaft 41 and the mid-PTO shaft 33 canbe minimized. Also, the arrangement, where the running powertransmission mechanism 50 is located on the front side of thetransmission case 60 along the vehicle lengthwise direction, and themid-PTO power transmission gear train 43 for connection between the PTOpower transmission shaft 41 and the mid-PTO shaft 33 is located on therear side of the transmission case 60, enables the mid-PTO powertransmission gear train 43 to be located along an imaginary straightline between the PTO power transmission shaft 41 and the mid-PTO shaft33. Such a linear arrangement enables the mid-PTO power transmissiongear train 43 to be greatly reduced in size and simplified in structure.

Also, in the transmission 30, the rear PTO gear train 42, whichtransmits the driving power from the PTO power transmission shaft 41 tothe rear PTO shaft 32, is provided with the idle gear 42 b and theintermediate shaft 42 c, and these members are located closer to thefirst lateral side than the PTO power transmission shaft 41 along thevehicle width direction. Whereby, it is possible to transmit the drivingpower with its speed reduced, from the PTO power transmission shaft 41to the rear PTO shaft 32, while effectively limiting the size of thetransmission case 60.

That is, in a general application, the transmission of driving powerfrom the PTO power transmission shaft 41 to the rear PTO shaft 32 mustbe done with the reduction of its speed. If the rear-PTO gear member 42a supported on the PTO power transmission shaft 41 is directly meshedwith the final gear 42 e supported on the rear PTO shaft 32, a pitchradius of the rear-PTO gear member 42 e must be increased, which leadsto increase of the distance between the PTO power transmission shaft 41and the rear PTO shaft 32 and hence invites increased size of thetransmission case 60.

In light of the above problems, the idle gear 42 b and the intermediateshaft 42 c are interposed between the rear-PTO gear member 42 a and thefinal gear 42 e, while the idle gear 42 b and the intermediate shaft 42c are located closer to the first lateral side of the transmission case60 than the PTO power transmission shaft 41 is, as described above. Thatis, as illustrated in FIG. 7, the PTO power transmission shaft 41 islocated in the transmission case 60 closer to the second lateral sidethereof than the PTO input shaft 31 and the running power input shaft 34with respect to the vehicle width direction and between both the inputshafts 31, 34 with respect to the vertical direction. In thisarrangement, the running power transmission mechanism 50 is located onlyin a space of the transmission case 60 closer to the first lateral sideand lower side thereof than the running power input shaft 34 is, asdescribed above. Accordingly, there exists an empty space in thetransmission case 60 closer to the rear side of the transmission case 60along the vehicle lengthwise direction, and closer to the first lateralside than the PTO power transmission shaft 41.

In the transmission 30, the idle gear 42 b and the intermediate shaft 42c are placed within the aforesaid empty space, thereby effectivelypreventing the increase in size of the transmission case 60, whileachieving transmission of the driving power with its speed reduced fromthe PTO power transmission shaft 41 to the rear PTO shaft 32.

The vehicle 100 of this embodiment includes the hydraulic lift unit 400for elevating a working unit such as a cultivating unit disposed on therear side of the chassis 10, valve unit 410 for controlling feeding anddischarging of pressurized fluid to the hydraulic lift unit 400,auxiliary pump 420 for feeding pressurized fluid to the valve unit 410,and auxiliary-pump power transmission mechanism 430 for transmittingdriving power from the PTO input shaft 31 to the auxiliary pump 420.

As best illustrated in FIGS. 3–5, the hydraulic lift unit 400 includescylinder tube 401 located along the vehicle lengthwise direction, pistonhead 402 reciprocably and fluid-tightly mounted in the cylinder tube401, piston rod 403 having a front end connected with the piston head402 and a rear end rearwardly extending through a rear opening of thecylinder tube 401, support shaft 404 supported along the vehicle widthdirection, arm 405 having a proximal end relatively non-rotatablysupported on the support shaft 404 and a distal end connected with therear end of the piston rod 403, and a pair of lift arms 406 havingproximal ends relatively non-rotatably supported on the support shaft404 and distal ends extending to the rear side of the chassis. Accordingto this arrangement, the pair of lift arms 406 can be pivotally movedabout the axis of the support shaft 404 by the hydraulic action ofpressurized fluid applied on the piston head 402.

Reference code 405 a in FIG. 4 represents a spacer for fixedlypositioning the arm 405. Reference code 60 f in FIG. 4 represents abreather pipe for communication between an inside air layer of thetransmission case 60 and ambient air for absorbing volume variation dueto temperature change of reservoir fluid.

Now, the description will be made in detail for mounting positions ofthe cylinder tube 401, the valve unit 410 and the auxiliary pump 420.

First, the description will be made for the position of the cylindertube 401 with respect to the vertical direction. The cylinder tube 401is located above the PTO input shaft 31 (or the input shaft 21 a),thereby preventing interference with the PTO power transmissionmechanism 40. Positioning of the cylinder tube 401 above the PTO inputshaft 31 as intended herein includes positioning of the cylinder tube401 above the PTO input shaft 31 within the transmission case 60 and onthe top surface of the transmission case 60 in abutting relationshipwith each other.

With respect to the width direction, the cylinder tube 401 is located inthe transmission case 60 closer to the first lateral side thereof alongthe vehicle width direction. The cylinder tube 401 also has a frontopening, which is closed with the valve unit 410. The cylinder tube 401and the valve unit 410 are aligned in series along the lengthwisedirection of the vehicle in the transmission case 60 closer to the firstlateral side.

Preferably, recess 410′ is formed on a surface of the valve unit 410facing the cylinder tube 401 for receiving the cylinder tube 401,thereby achieving improved efficiency in assembling the valve unit 410and the cylinder tube 401.

On the other hand, the auxiliary pump 420 is supported within thetransmission case 60 so as to be located closer to the second lateralside thereof than the valve unit 410 and the cylinder tube 401 are.

Thus, the arrangement of this embodiment, where, in the transmissioncase, the valve unit 410 and the cylinder tube 401 are located closer tothe first lateral side of the transmission case 60, while the auxiliarypump 420 is located closer to the second lateral side of the same,produce desirable effects as described below.

In the conventional working vehicle, the valve unit and the cylindertube are located on a top surface of the transmission case along thevehicle lengthwise direction, while the auxiliary pump for feedingpressurized fluid to the valve unit is supported on a rear wall of thetransmission case. Accordingly, where reservoir fluid within thetransmission case is to be fed to the cylinder tube, the reservoir fluidmust be once drawn from a lower portion of the transmission case to arear side, and then fed to the cylinder tube via the valve unit on thetop surface of the transmission case. This poses a problem of causing anelongated fluid distribution path. This elongation of the fluiddistribution path invites enlargement of a hydraulic pump forcompensation of loss of pressure, enlargement of the vehicle due tolarge occupation of conduit arrangement, deterioration of response rateof a hydraulic power unit due to lowered rate of feeding pressurizedfluid to the hydraulic power unit, or any other undesirable problems.

To address the above problems, as described in this embodiment, thevalve unit 410 and the cylinder tube 401 are aligned in series along thevehicle lengthwise direction in the transmission case 60 closer to thefirst lateral side, and the auxiliary pump 420 is located within thetransmission case 60 closer to the second lateral side thereof than thevalve unit 410 and the cylinder tube 401 are. Hence, this arrangementcan shorten the fluid distribution path for feeding working fluid fromthe transmission case 60 to the valve unit 410 through the auxiliarypump 420, thereby achieving downsizing of the auxiliary pump 420,downsizing of the vehicle and improved response rate of the hydraulicpower unit.

The transmission case 60 is preferably provided withreservoir-fluid-take-off port 65 (see FIGS. 2 and 3) that is locatedsubstantially at the same portion as that of the auxiliary pump 420 withrespect to the vehicle lengthwise direction so as to be fluidlyconnected with a suction port of the auxiliary pump 420. Thisarrangement achieves a further shortening of the fluid distributionpath.

FIG. 11 is a cross section taken along lines XI—XI in FIG. 3. Asillustrated in FIGS. 3 and 11, it is more preferable to provide strainer66 that is located below the middle chamber C2 within the transmissioncase 60 and held between the body 61 and the side cover 64 in a clampedrelationship, so that reservoir fluid is taken off from thereservoir-fluid-take-off port 65 through the strainer 66. Whereby,impurities such as iron powders can effectively be removed. Thereservoir-fluid-take-off port 65 is formed in a cover detachablyattached to the body 61 so as to cover a side opening formed in the body61. With this arrangement, the strainer 66 within the transmission case60 can be accessed from the outside by removing the cover.

In this embodiment, as illustrated in FIGS. 3–5, the body 61 of thetransmission case 60 is integrally formed with first bulging portion 61,which bulges upward from the body 61 at a portion closer to the firstlateral side of the transmission case 60, and the cylinder tube 401 islocated within this first bulging portion 61 c in an attempt to lowerthe vehicle height by lowering the mounting position of the cylindertube 401.

That is, the arrangement with the cylinder tube mounted on the topsurface of the transmission case causes an necessities to prepare anadditional part for supporting the cylinder tube and mount the cylindertube at a higher place. Accordingly, it is likely to invite problemssuch as increased manufacturing cost due to increase in number of parts,and increased vehicle height. Generally, a driver's seat is locatedabove the cylinder tube (see FIG. 1), so that the mounting of thecylinder tube at a higher place increases the height at which thedriver's seat is mounted. This invites increased height of gravitationalcenter of the vehicle and hence difficulty in getting on and off thedriver's seat.

Contrarily to the above, in this embodiment, the cylinder tube 401 isplaced within the first bulging portion 61 c of the transmission case60, thereby enabling the cylinder tube 401 to be mounted at a lowerplace with a secured support.

The arrangement with the cylinder tube 401 placed within thetransmission case 60 also omits a necessity to provide a specialmechanism for supporting the supporting shaft 404 on the transmissioncase 60. Hence, the support shaft 404 can be securely supported withinthe transmission case 60 with maintaining the manufacturing cost withina low level.

In this embodiment, as best illustrated in FIG. 4, the support shaft 404is supported by the transmission case 60 so as to have opposite endsrespectively and outwardly extending through both the lateral walls ofthe transmission case 60 to have outward extensions respectivelyconnected with the pair of the lift arms 406.

Preferably, as best illustrated in FIGS. 3 and 7, the first bulgingportion 61 c has a bottom wall, on which lip 61 d is provided to preventthe cylinder tube 401 from slipping rearward. As a result, the cylindertube 401 can be held by the valve unit 410 and the lip 61 d for moresecured support of the cylinder tube 401.

The auxiliary-pump power transmission mechanism 430 is placed within thefront chamber C1. Specifically, as illustrated in FIGS. 6 and 9, theauxiliary-pump power transmission mechanism 430 includes gear train 431that in turn includes driving-side gear 431 a relatively non-rotatablysupported on the PTO input shaft 31, idle gear 431 b meshed with thedriving-side gear 431 a, and driven-side gear 431 c relativelynon-rotatably supported on pump shaft 421 of the auxiliary pump 420 inmeshed engagement with the idle gear 431.

As best illustrated in FIG. 6, the gear train 431 is located above andon the right hand side of the PTO input shaft 31, thereby preventinginterference with the PTO power transmission mechanism 40 including thePTO power transmission shaft 41 located below and on the right hand sideof the PTO input shaft 31, and with the running power transmissionmechanism 50 located on the left hand side of the running power inputshaft 34, while achieving effective use of the space within thetransmission case 60.

That is, in this embodiment, the PTO input shaft 31 and the runningpower input shaft 34 are aligned along the widthwise center line of thetransmission case 60 in parallel adjacent relationship with each other,while the auxiliary-pump power transmission mechanism 430 driven by thePTO input shaft 31 and the PTO power transmission mechanism 40 alignedin vertically spaced apart relationship with each other are locatedcloser to the first lateral side of the transmission case 60. Also, therunning power transmission mechanism 50 driven by the running powerinput shaft 34 is located only in a space of the transmission case 60closer to the second lateral side and lower side thereof. Whereby,effective use of the space within the transmission case 60 can beachieved by preventing mutual interference between these powertransmission mechanisms.

Preferably, as illustrated in FIGS. 4 and 6, in a space of the body 61of the transmission case 60 closer to its lateral side opposite to theside, closer to which the first bulging portion 61 c is located, isprovided second bulging portion 61 e, which bulges upward from the body61 and is adapted to be closed by the front cover 62 so as to supportthe auxiliary pump 420 thereon. Whereby, it is possible to securelysupport the auxiliary pump 420 and reduce the manufacturing cost byreducing the number of parts.

More preferably, the gear train 431 is partly placed within the closedspace defined by the second bulging portion 61 e and the front cover 62.

While variations are possible, in this embodiment, opening 61 e′communicated with the closed space defined by the front cover 62 and thesecond bulging portion 61 e is formed in the second bulging portion 61e, enabling the pump shaft 421 to extend into the closed space from therear side through the opening 61 e′ and be relatively non-rotatablyconnected with the driven-side gear 431 c (see FIG. 4).

As illustrated in FIG. 16, as an alternative to the second bulgingportion 61 e, there may be provided pump mounting cover 425 connected toa front side of the front cover 62, thereby defining the closed space incooperation with the front cover 62, and opening 425′ communicated withthe closed space is formed in the pump mounting cover 425, enabling thepump shaft 421 to extend into the closed space from the front sidethrough the opening 425′.

As illustrated in FIG. 17, where the auxiliary hydraulic pump 420(hereinafter described) is in the form of a double-headed pump with itsdouble pump heads aligned in tandem, openings 425′ and 62′ communicatedwith the closed space may be respectively formed in the pump mountingcover 425 and the front cover 62, and pump shafts 421′, 421″ areextended into the closed space through these openings from the frontside of the pump mounting cover 425 and the rear side of the front cover62, thereby arranging the double pump heads 420′, 420″ along the vehiclelengthwise direction. Alternatively, in use of the transmission havingthe above mentioned bulging portion, both the double pump heads 420′,420″ may be located on either front or rear side of the bulging portion.

Now, the description will be made for a hydraulic circuit of thetransmission arrangement according to this embodiment.

FIG. 12 is a hydraulic circuit diagram of the hydraulic lift unit 400and the valve unit 410. FIG. 13 is a hydraulic circuit diagram of thecenter section and the PTO clutch unit. FIG. 14 is a longitudinalcross-section of the center section in front elevation.

The reservoir-fluid-take-off port 65 of the transmission case 60 isconnected with suction port 420 a of the auxiliary pump 420 installed onthe top surface of the transmission case 60 via conduit 501 (see FIG.2). That is, reservoir fluid within the transmission case 60 is filteredby the strainer 66 mounted within the middle chamber C2 of thetransmission case 60, and then is sucked into the suction port 420 a ofthe auxiliary pump 420 via the reservoir-fluid-take-off port 65 and theconduit 501.

Pressurized fluid discharged from outlet port 420 b of the auxiliarypump 420 is fed into suction port 410 a of the valve unit 410 alignedwith the auxiliary pump 420 along the vehicle width direction via theconduit 502 (see FIG. 2).

The valve unit 410 forms therein inlet line 411 branched into first andsecond lines 412, 413 via flow dividing valve with its proximal endcommunicated with the suction port 410 a provided on the top surface ofthe valve unit 410 and distal end incorporated into the valve unit 410.

In this embodiment, auxiliary control valve unit 450 is connected with aside wall of the valve unit 410 so as to selectively take offpressurized fluid flowing in the first line 412 via plural take-offports. That is, the auxiliary control valve unit 450 enables pressurizedfluid flowing in the first line 412 to be used for a hydraulic powerunit or the like for elevating the bucket unit 111 (see FIG. 1), andtilting the same to a dump position.

As illustrated in FIGS. 4 and 12, the auxiliary control valve unit 450includes unit body 451, a plurality of hydraulic lines 452 formed in theunit body 451, and at least one switch valve 453 (two in thisembodiment) interposed in the plurality of hydraulic lines 452, so thatpressurized fluid introduced through one of the hydraulic lines can betaken off through a plurality of take-off ports 450 a. In thisembodiment, two of the plurality of take-off ports 450 a are formed inthe top surface of the valve unit 410 (see FIG. 4).

The first line 412 has an end opening to the outside through the sidewall of the valve unit via high-pressure relief valve 414 for settinghydraulic pressure of the first line 412 and communicated with one ofthe hydraulic lines of the auxiliary control valve unit 450.

The valve unit 410 is designed to be capable of closing the frontopening of the cylinder tube 401 with its recess 410′, as describedabove.

The valve unit 410 is also provided with working-fluid line 415 (seeFIGS. 3, 4 and 12) that has a proximal end communicated with the firstline 412 via the auxiliary control valve unit 450 and a distal endopening to the inside of the cylinder tube 401 via the recess 410′.

In the working-fluid line 415 is interposed elevational-movement switchvalve 416 and stop valve 417, both of which are designed to be capableof being operated from the outside. The stop valve 417 is equipped withslow-return valve 418 for preventing abrupt downward movement of thelift arms 406 (see FIG. 12).

In this embodiment, as best illustrated in FIG. 3, the stop valve 417 islocated in a horizontal orientation, while operating member 417 athereof is located in an upwardly slanting orientation. Specifically,the stop valve 417 is connected with the operating member 417 a viauniversal joint 417 b, which has a driving-side member supported in anupwardly slanting orientation by stay 417 c secured on the valve unit410.

Reference code 416 a in FIGS. 4 and 5 represents a link mechanism foroperating the elevational-movement switch valve 416, which is connectedwith elevational-movement operating lever 416 b for switching the switchvalve 416 to any one of “RAISE”, “NEUTRAL”, and “LOWER”. Actions takenby the lift arms 406 are fed back to the elevational-movement operatinglever 416 b, so that where an end of the lift arms 406 reaches apredetermined upper limit (or lower limit) upon switching the switchvalve 416 from the neutral position to the raising position (or loweringposition), an action of the lift arms 406 is fed back to theelevational-movement operating lever 416 b, which is then forced toreturn to the neutral position.

Reference code 419 in FIGS. 4, 5 and 12 represents a drain line forreturning drained fluid discharged through the elevational-movementswitching valve 416 into the transmission case 60. In this embodiment,the drain line 419 is open to the first bulging portion 61 c, so thatdrained fluid is flown from the first bulging portion 61 c into the rearchamber C3 of the transmission case 60. More preferably, the rearchamber C3 is provided with inner wall 61 f for temporarily receivingreturn fluid from the drain line 419 (see FIG. 3). This inner wall 61 fcan cool return fluid heated to a high temperature coming from the drainline 419.

On the other hand, the second line 413 has a distal end communicatedwith discharge port 410 b formed in the top surface of the valve unit410, to which optionally provided hydraulic circuit 500 forpower-steering unit, hydraulic circuit 600 for the PTO clutch unit 70,and first charge line 23 d of the HST are connected through conduit 503(see FIGS. 4, 12 and 13).

In this embodiment, hydraulic fluid discharged from the single auxiliarypump 420 is divided into first and second lines 412, 413 by using theflow dividing valve. In this respect, where temperature rise inhydraulic fluid accompanied by the operation of the flow dividing valveposes a problem, it is possible to omit the flow dividing valve andalternatively employ the arrangement where the double headed pump withits heads 420′, 420″ connected in tandem is employed as the auxiliarypump 420, while a discharge port of one pump head 420′ is connected withthe first line 412 and a discharge port of another pump head 420″ isconnected with the second line 413, as illustrated in FIG. 18. Thus, theproblem as mentioned above can be resolved.

As illustrated in FIG. 13, the hydraulic circuit 600 for the PTO clutchunit includes suction line 601 that has a proximal end directlycommunicated with the end of the second line 413 or indirectlycommunicated with the same via the hydraulic circuit 500 for thepower-steering unit, PTO line 602 and HST line 603 branched from thesuction line 601, switch valve 604 interposed in the PTO line 602, andhigh-pressure relief valve 605 interposed in the HST line 603.

In this embodiment, as illustrated in FIG. 5, valve assembly 650 mainlyconstituting the hydraulic circuit 600 for the PTO clutch unit isinstalled on an upper outer surface of the side cover 64 of thetransmission case 60.

Specifically, the valve assembly 650 is provided with inlet port 600 a,into which pressurized fluid is fed, the suction line 601 having an endcommunicated with the inlet port 600 a, the PTO line 602 and the HSTline 603 branched from the suction line 601, the switch valve 604interposed in the PTO line 602, the high-pressure relief valve 605interposed in the HST line 603, and outlet port 600 b communicated witha distal end of the HST line 603 (see FIGS. 5 and 12).

The PTO line 602 is communicated with the hole 615 formed in the sidecover 64 of the transmission case 60 (see FIG. 9). Whereby, pressurizedfluid fed from the PTO line 602 is adapted to be capable of affectingthe clutch pressing member 75 of the PTO clutch unit 70 and the brakepressing member 83 of the PTO brake mechanism 80 respectively throughthe clutch line 611 and the brake line 612, which are branched from thePTO line 602 by the manifold 616, which acts as pressurized-fluiddivider (see FIGS. 5 and 9).

The HST line 603 is communicated with the center section 23 throughconduit 504 connected with the outlet port 600 b (see FIGS. 6 and 13)and line filter 68, which is supported on a lower outer surface of thefront cover 62 with performing a bypass function necessary for copingwith clogging (see FIGS. 2, 3 and 6).

FIG. 15 is a front view of the transmission case 60 with the centersection removed. As illustrated in FIG. 15, the front cover 62 of thetransmission case 60 forms therein filter suction line 62 a that has afirst end communicated with the HST line 603 via the conduit 504 and asecond end communicated with suction port 68 a of the line filter 68,and filter discharge line 62 b that has a first end communicated withdischarge port 68 b of the line filter 68 and a second end opening tothe outside through a surface of the front cover 62 for supporting thecenter section. The second end of the filter discharge line 62 b openingto the outside forms first charge port 23 m (see FIGS. 13 and 15). Thefront cover 62 also forms therein suction line 23 p that has a first endopening to the outside through its supporting surface for supporting thecenter section to form second charge port 23 n and a second end openingto the inside of the transmission case 60.

As described above, in this embodiment, since the HST line 603 is fedwith working fluid which is filtered by the strainer 66 located in thetransmission case 60, the line filter 68 may be manufactured in reducedsize. That is, if iron powders or the like are contained in the HST line603, they may invite malfunction or any other problems in the HST 20located on the downstream side. To address this problem, a large-sized,high-performance line filter must usually be provided. On the contrary,in this embodiment, the strainer 66 is provided to filter working fluidto some extent, as described above, so that the number of times by whichan expensive line filter must be replaced with a new one can bedrastically reduced, and a large-sized filter with such a highperformance required in the conventional arrangement is not required.Even if the line filter 68 is clogged, hydraulic fluid sucked flows intothe HST 20, bypassing the line filter 68. As a result, there may occurno destruction of the HST 20.

As illustrated in FIGS. 13 and 14, the center section 23 is providedwith a pair of hydraulic lines 23 a, 23 a′ for hydraulic connectionbetween the hydraulic pump body 21 and the hydraulic motor 22 of the HST20, first and second bypass lines 23 b, 23 c for connection between thepair of hydraulic lines 23 a, first charge line 23 d with its first endcommunicated with the first charge port 23 m and second end communicatedwith the first bypass line 23 b, check valve 23 e interposed in thefirst bypass line 23 b between its connection point with first hydraulicline 23 a and connection point with the charge line 23 d, check valve 23f with a throttle valve, which is interposed in the bypass line 23 bbetween its connection point with second hydraulic line 23 a′ andconnection point with the charge line 23 d, a pair of high-pressurerelief valve 23 g with a check valve, which are interposed in the secondbypass line 23 c, charge relief valve 23 h interposed in the firstcharge line 23 d for setting a maximum hydraulic pressure in the firstcharge line 23 d, second charge line 23 i with its first endcommunicated with the second charge port 23 n and second end connectedwith the first charge line 23 d, suction check valve 23 j interposed inthe second charge line 23 i, and discharge line 23 k for dischargingrelief fluid from the charge relief valve 23 h into the HST casing 24.

The center section 23 also forms therein drain hole 231 that is locatedabove the pump shaft 21 a, and has a first end opening to the inside ofthe HST casing 24 and a second end opening to the outside through anabutting surface against the front cover 62 (see FIGS. 9, 13 and 14).More specifically, the front cover 62 forms therein communication hole62 c for communication between the drain hole 231 and the front chamberC1 of the transmission case 60, so that drain fluid discharged into theHST casing 24 flows into the front chamber C1 of the transmission case60. Also, an entrance port of the suction check valve 23 j opening tothe outside of the center section 23 is formed in the center section 23as being located below the motor shaft 22 a and communicated with thesecond charge port 23 n of the front cover 62 in a face-to-facerelationship with each other.

The second charge line 23 i and the suction valve 23 j are to preventoccurrence of negative pressure in the pair of hydraulic lines 23 a, 23a where the vehicle is parked on a slope with its engine stopped,thereby preventing the vehicle from rolling down the slope (free wheelphenomenon).

In the power transmission arrangement according to this embodiment,pressurized fluid from the auxiliary pump 420 is fed to the hydrauliclift unit 400, the power-steering unit, the HST 20, the PTO brakemechanism 80 and the PTO clutch unit 70 in an attempt to reduce thenumber of parts by omitting the necessity to provide an additional pumpand hence achieve downsizing and low manufacturing cost of the vehicle.

Now, the description will be made for circulation path of hydraulicfluid reserved in the transmission case 60.

The reserved hydraulic fluid within the transmission case 60 is suckedinto the auxiliary pump 420 via the strainer 66 located below the middlechamber C2 in the transmission case 60. Pressurized fluid dischargedfrom the auxiliary pump 420 is branched into the first line 412 and thesecond line 413.

Primarily, pressurized fluid branched off into the first line 412 actsas working fluid for the hydraulic lift unit 400. Return fluid from thehydraulic lift unit 400 is returned into the rear chamber C3 via thefirst bulging portion 61 c, as described above. The return fluid intothe rear chamber C3 is then cooled through the inner wall 61 f in thisembodiment. The return fluid returned into the rear chamber C3 flowsinto the middle chamber C2 via the fluid communication opening 61 y, asacting as lubricant for members placed within the rear chamber C3, suchas the rear PTO gear train 42 and the mid-PTO power transmission geartrain 43. Then, it is again sucked into the auxiliary pump 420.

On the other hand, pressurized fluid branched off into the second line413 is fed into the HST 23 as replenishing fluid via the optionallyprovided power-steering unit and the PTO clutch unit 70. Return fluidfrom the HST 23 is returned into the front chamber C1 of thetransmission case 60, as described above. Then, this return fluid in thefront chamber C1, which then flows out of the front chamber C1 as actingas lubricant for members placed within the front chamber C1, such as therunning power transmission mechanism 50, the PTO clutch unit 70, thefront-wheel-driving-power-take-off unit 53 and the auxiliary-pump powertransmission mechanism 430, and passes the intermediate chamber C4, onceflows into the rear chamber C3 via the fluid communication opening 61 x,then flows into the middle chamber C2 via the fluid communicationopening 61 y, and is again sucked into the auxiliary pump 420.

Thus, in this embodiment, return fluid of high temperature from the HST23, the hydraulic lift unit 400 or the like is prevented fromcirculating without some detouring, thereby effectively preventingdeterioration in operational efficiency of the HST, the hydraulic liftunit and the like.

That is, return fluid from the HST 23, the hydraulic lift unit 400 orthe like is heated to high temperature, which imparts a low viscosity tothe return fluid. Accordingly, if the return fluid with a low viscosityis simply returned, there may cause increase in the amount of leakage ofhydraulic fluid through respective positions of the auxiliary pump 420,the HST 23 and the hydraulic lift unit 400, which results indeteriorated efficiency of the hydraulic pump, HST and/or hydraulicpower unit.

On the contrary, in this embodiment, hydraulic fluid is so circulatedthat a stream of return fluid from the HST 23 and a stream of the samefrom the hydraulic lift unit 400 respectively flow into the frontchamber C1 and the rear chamber C3, then return to the middle chamber C2and then again flow out of the middle chamber C2 for circulation.Accordingly, return fluid of high temperature is sufficiently cooledbefore flowing into the middle chamber C2, thereby preventing theaforementioned adverse effects caused by circulation of the hightemperature fluid.

According to a more preferable arrangement, the brake mechanism 210 isplaced within the intermediate chamber C4, which is located within thetransmission case 61 closer to the first lateral side than the middlechamber C2 along the vehicle width direction, while the intermediatechamber C4 is so constructed as to enable hydraulic fluid to flow fromthe front chamber C1 thereinto and then flow out into the middle chamberC2 (see FIG. 8). Whereby, hydraulic fluid is unlikely to stay within theintermediate chamber C4, so that friction heat generated during theoperation of the brake mechanism 210 can effectively be released. As aresult, it is possible to achieve downsizing of the unit and improveddurability.

Reference code 61 z in FIG. 8 represents a fluid communication hole forcommunication between the front chamber C1 and the intermediate chamberC4. Reference code 62 d in FIG. 6 represents fluid tap threaded into anopening formed in the front cover 62. The fluid tap 62 d is preferablylocated above the auxiliary-pump power transmission mechanism 430.

This specification is by no means intended to restrict the presentinvention to the preferred embodiments set forth therein. Variousmodifications to the power transmission arrangement and the transmissionfor a working vehicle, as described herein, may be made by those skilledin the art without departing from the spirit and scope of the presentinvention as defined in the appended claims.

1. A transmission of a working vehicle for divergingly transmittingdriving power from an engine to a working unit and driving wheels,comprising: a transmission case that is disposed to be apart from saidengine in a vehicle lengthwise direction, a valve unit for controllingfeeding and discharging pressure oil to/from a hydraulic power unit foroperating said working unit, and an auxiliary pump for supplying thepressure oil to said valve unit, wherein said valve unit and saidauxiliary pump are supported by said transmission case so as to beoverlapped with respect to their positions in the vehicle lengthwisedirection.
 2. A transmission of a working vehicle for diverginglytransmitting driving power from an engine to a working unit and drivingwheels, comprising: a transmission case that is disposed to be apartfrom said engine in a vehicle lengthwise direction, the transmissioncase being provided with a reservoir oil discharge port for taking outoil reserved in its interior at a front side thereof, a valve unit forcontrolling feeding and discharging pressure oil to/from a hydraulicpower unit for operating said working unit, and an auxiliary pump forsupplying the pressure oil to said valve unit, wherein said auxiliarypump is provided at a front side of the transmission case while saidauxiliary pump and said reservoir oil discharge port are in fluidconnection through an external conduit.
 3. A transmission of a workingvehicle for divergingly transmitting driving power from an engine to aworking unit and driving wheels, comprising: a transmission case that isdisposed to be apart from said engine in a vehicle lengthwise direction,the transmission case being provided with a reservoir oil discharge portfor taking out oil reserved in its interior at a front side and a lowerside thereof, a valve unit for controlling feeding and dischargingpressure oil to/from a hydraulic power unit for operating said workingunit, the valve unit being supported at a front side of saidtransmission case and at a position upward of the reservoir oildischarge port, an auxiliary pump for supplying the pressure oil to saidvalve unit, the auxiliary pump being supported at a front side of saidtransmission case and at a position upward of said reservoir oildischarge port, and a HST supported at a front surface of saidtransmission case, wherein an external conduit for fluid connectionbetween said reservoir oil discharge port and said auxiliary pump isdisposed sideward of the HST.
 4. A transmission of a working vehicleaccording to claim 1, wherein the transmission case is provided with areservoir oil discharge port at a front side and downward thereof fortaking out oil reserved in its interior, wherein said auxiliary pump andsaid valve unit are supported upward of the reservoir oil discharge portand at a front side of said transmission case, and wherein saidauxiliary pump and said reservoir oil discharge port are disposed at thesame positions with respect to a vehicle width direction.
 5. Atransmission of a working vehicle according to claim 2, wherein saidreservoir oil discharge port is disposed at a front side and downward ofsaid transmission case, wherein said auxiliary pump is supported upwardof the reservoir oil discharge port and at a front side of saidtransmission case, and wherein said auxiliary pump and said reservoiroil discharge port are disposed at the same positions with respect to avehicle width direction.
 6. A transmission of a working vehicleaccording to claim 3, wherein said auxiliary pump and said reservoir oildischarge port are disposed at the same positions with respect to avehicle width direction.
 7. A transmission of a working vehicleaccording to claim 1, further comprising: a HST supported at a frontsurface of said transmission case, the HST receiving pressure oil fromsaid auxiliary pump as charge oil, and a line filter interposed betweensaid auxiliary pump and said HST, wherein said valve unit and saidauxiliary pump are disposed at an upper and front side of saidtransmission case so as to be positioned adjacent to the HST, whereinsaid reservoir oil discharge port is disposed at a lower side of thetransmission case, and wherein said line filter is supported at a frontsurface of said transmission case at a position downward of the HST. 8.A transmission of a working vehicle according to claim 2, furthercomprising: a HST supported at a front surface of said transmissioncase, the HST receiving pressure oil from said auxiliary pump as chargeoil, and a line filter interposed between said auxiliary pump and saidHST, wherein said valve unit and said auxiliary pump are disposed at anupper and front side of said transmission case so as to be positionedadjacent to the HST, wherein said reservoir oil discharge port isdisposed at a lower side of the transmission case, and wherein said linefilter is supported at a front surface of said transmission case at aposition downward of the HST.
 9. A transmission of a working vehicleaccording to claim 3, wherein pressure oil from said auxiliary pumpthrough a line filter is utilized as charge oil for said HST, andwherein said line filter is supported at a front surface of saidtransmission case at a position downward of the HST.
 10. A transmissionof a working vehicle according to claim 7, wherein said line filter isdisposed along the vehicle lengthwise direction.
 11. A transmission of aworking vehicle according to claim 8 wherein said line filter isdisposed along the vehicle lengthwise direction.
 12. A transmission of aworking vehicle according to claim 9, wherein said line filter isdisposed along the vehicle lengthwise direction.
 13. A transmission of aworking vehicle according to claim 10, wherein a strainer is disposedwithin said transmission case at a position adjacent to said line filteralong the vehicle width direction, and wherein the auxiliary pump isarranged so as to take out the reservoir oil within said transmissioncase through said strainer.
 14. A transmission of a working vehicleaccording to claim 11, wherein a strainer is disposed within saidtransmission case at a position adjacent to said line filter along thevehicle width direction, and wherein the auxiliary pump is arranged soas to take out the reservoir oil within said transmission case throughsaid strainer.
 15. A transmission of a working vehicle according toclaim 12, wherein a strainer is disposed within said transmission caseat a position adjacent to said line filter along the vehicle widthdirection, and wherein the auxiliary pump is arranged so as to take outthe reservoir oil within said transmission case through said strainer.16. A transmission of a working vehicle according to claim 1, wherein astrainer is disposed within said transmission case along a vehicle widthdirection, and wherein said auxiliary pump is arranged so as to take outthe reservoir oil within said transmission case through said strainer.17. A transmission of a working vehicle according to claim 2, wherein astrainer is disposed within said transmission case along a vehicle widthdirection, and wherein said auxiliary pump is arranged so as to take outthe reservoir oil within said transmission case through said strainer.18. A transmission of a working vehicle according to claim 3, wherein astrainer is disposed within said transmission case along a vehicle widthdirection, and wherein said auxiliary pump is arranged so as to take outthe reservoir oil within said transmission case through said strainer.19. A transmission of a working vehicle according to claim 1, wherein astrainer is disposed within said transmission case along a vehicle widthdirection in a state of being detachable through a side opening formedin said transmission case, and wherein said side opening is covered by acover detachably connected to the transmission case, said cover beingprovided with a reservoir oil discharge port for taking out oil reservedin said transmission case through said strainer.
 20. A transmission of aworking vehicle according to claim 2, wherein a strainer is disposedwithin said transmission case along a vehicle width direction in a stateof being detachable through a side opening formed in said transmissioncase, and wherein said reservoir oil discharge port is formed in a coverdetachably connected to the transmission case so as to cover said sideopening.
 21. A transmission of a working vehicle according to claim 3,wherein a strainer is disposed within said transmission case along avehicle width direction in a state of being detachable through a sideopening formed in said transmission case, and wherein said reservoir oildischarge port is formed in a cover detachably connected to thetransmission case so as to cover said side opening.